Epoxide groups are an effective way to impart polarity into unsaturated polymers, particularly unsaturated elastomers. The manufacturing of epoxidized elastomers generally requires long reaction times, the use of excess starting materials, the use of solvents, the use of catalysts and/or subsequent finishing through a basic medium prior to packaging resulting in high costs to produce. As a result, only epoxidized natural rubber is available commercially.
United States Patent Publication US 2014/357794 describes a method of functionalizing an elastomer, the first step of which is epoxidation. Therein, US 2014/357794 describes a typical epoxidation process in which the elastomer is treated with meta-chloroperoxybenzoic acid (mCPBA) in solution at reduced temperature (0° C.) for 6 hours in the presence of a catalyst.
United States Patent Publication US 2007/0276062 describes a process for producing an epoxidized elastomeric polymer in which at least one elastomeric polymer containing ethylenic unsaturation is mixed with at least one hydrogen peroxide precursor and at least one carboxylic acid or derivative thereof in the presence of water.
Chinese Patent Publication CN 1290709 describes a catalytic epoxidized reaction process for elastomers containing double bonds by reaction an alkyl hydrogen peroxide and the elastomer in the presence of a catalyst (i.e. a transition metal complex) without a solvent. This process specifically excludes peracid epoxidation systems.
Poly(isobutylene-co-isoprene), or IIR, is a synthetic elastomer commonly known as butyl rubber which has been prepared since the 1940's through the random cationic copolymerization of isobutylene with small amounts of isoprene (1-5 mole %). As a result of its molecular structure, IIR possesses superior air impermeability, a high loss modulus, oxidative stability and extended fatigue resistance.
Butyl rubber is understood to be a copolymer of an isoolefin and one or more, preferably conjugated, multiolefins as comonomers. Commercial butyl comprises a major portion of isoolefin and a minor amount, usually not more than 2.5 mol %, of a conjugated multiolefin. Butyl rubber or copolymer is generally prepared in a slurry process using methyl chloride as a diluent and a Friedel-Crafts catalyst as part of the polymerization initiator. This process is further described in U.S. Pat. No. 2,356,128 and Ullmanns Encyclopedia of Industrial Chemistry, volume A 23, 1993, pages 288-295, the entire contents of which are herein incorporated by reference.
A fast, efficient and cost-effective process for the epoxidation of unsaturated polymers, especially butyl rubber, is still desired.